MKS 937B Operation Manual
41
Figure 6-7 Hot cathode setup information displayed on 937B LCD screen.
Gas Symbol Relative correction factor to N
2
Air
1.00
Argon
Ar 1.29
Carbon Dioxide
CO
2
1.42
Deuterium
D
2
0.35
Helium
He 0.18
Hydrogen
H
2
0.46
Krypton
Kr 1.94
Neon
Ne 0.30
Nitrogen
N
2
1.00
Nitrogen Oxide
NO 1.16
Oxygen
O
2
1.01
Sulfur Hexafluoride
SF
6
2.50
Water
H
2
O 1.12
Xenon
Xe 2.87
Table 6-2 Relative ionization correction factor to N2 for different gases.
3. DG Time
Refers to the degas time set for a hot cathode gauge. The value can be set from 1 to 240 minutes
with a minimum step of 1 minute. The default value is 30 min.
4. Sensitivity
Indicates sensitivity of the hot cathode gauge. Its typical value is 9 Torr
-1
for the MKS Low Power
Nude sensor, and 12 Torr
-1
for the Mini BA gauges. These default values will be automatically
selected based on the type of sensor being detected if no user-defined sensitivity value is stored.
A user can change the sensitivity, and its valid range is 1 to 50 Torr
-1
. Once a user-defined
sensitivity is saved, this sensitivity value will be used as default value when powering up a same
type of hot cathode gauge.
If a user changes the sensitivity without a hot cathode gauge being connected, this user-defined
sensitivity value will be saved as the default sensitivity for all the HC sensor types.
5. EC
The Emission Current can be set to 20 uA, 100 uA, Auto20, or Auto100. When Auto is selected,
the emission current is either 20 uA or 100 uA when pressure is higher than 1x10
-4
torr, and
automatically switches to 1 mA when pressure is below 1x10
-4
torr. The default setting for the
Emission Current is 20 uA.
6. Protect SP
The Protect Setpoint is used to turn off the hot cathode high voltage based on its own pressure
readings. The valid protect setpoint range for a hot cathode is 1.0x10
-5
torr to 1.0x10
-2
torr. The
default value is 5.0x10
-3
torr. The Protect Setpoint is always enabled on 937B.
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